In the prior art, a gate drive circuit is usually formed on an array substrate through gate driver on array (GOA) technology during manufacturing of an array of a liquid crystal display panel, thereby realizing progressive scan driving of gate lines. Based on this technology, a bonding procedure of an external IC can be omitted, and the integration level of the liquid crystal display panel can be improved.
GOA circuit usually comprises multistage GOA units, each stage of GOA unit driving a corresponding horizontal scan line. Each stage of GOA unit mainly comprises a pull-up part, a pull-up control part, a transfer part, a key pull-down part, a pull-down holding part, a boost part for boosting an electrical potential, and a reset part for resetting the electrical potential.
The pull-up part is mainly used for outputting a clock signal as a gate signal. The pull-up control part controls a working time of the pull-up part, and is usually connected to a transfer signal outputted from a previous stage of GOA unit. The key pull-down part is used for pulling down the gate signal to a low potential, and the pull-down holding part is used for keeping the gate signal and a control signal of a pull-up circuit at low potential.
In addition, since low temperature poly-silicon (LTPS) arises, GOA circuits present evident differences in frameworks and types, and can be generally divided into circuit types including NMOS, PMOS, and CMOS. In the manufacturing process of CMOS, as many as 12 photomasks will be used, and for NMOS and PMOS, which are unipolar transistors, 9 photomasks or less will be used. Therefore, in order to save production cost, unipolar LTPS-based GOA circuit is widely used.
A conventional unipolar LTPS-based GOA circuit usually uses a single unit pull-down holding part. However, the long working time of the pull-down holding part would have adverse influence on the service life of the circuit. Furthermore, as for a large size LTPS display panel, due to large RC load of the GOA circuit, the service life thereof will also be shortened.